Hydrothermal serpentine in a Hess Deep sediment core

Schmitz, W.; Singer, Arieh; Bäcker, H.; Stoffers, Peter

doi:10.1016/0025-3227(82)90149-9

Cited by 19 publications

(7 citation statements)

References 8 publications

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“…The pelagic unit is intrinsically heterogeneous and changes in com-position with depth. Minerals identified are calcite in several layers and nontronite, which is consistent with Schmitz et al (1982), who identified a smectite. Smectite can be formed by temperatures up to 200°C by hydrothermal alteration of basalt (Corliss et al, 1978;Mottl and Holland, 1978).…”

Section: Core 95supporting

confidence: 85%

Sediments and Their Geochemistry, Hess Deep

Eckhardt¹,

Puchelt²

1996

Proceedings of the Ocean Drilling Program, 147 Scientific Results

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Sediments from Hess Deep, Ocean Drilling Program Leg 147 Site 894, and from the deepest point of Hess Deep (recovered during cruise Sonne 60, core 95) were examined. Different lithologies within these sediments have different geochemical signatures. It is possible to distinguish the source rocks of the different sediment types and to reconstruct the processes affecting the genesis of the sediments. Foraminiferal ooze from Site 894 has high Sr concentrations and elevated but not constant Ba values. Sediments from lithic breccia sequences have nearly the same element concentrations and rare earth element (REE) patterns as underlying gabbroic rocks. The lithic breccias are a pure physical weathering product, exhibiting no alteration. Hydrothermal sediments from core 95 have varying concentrations of Mn, As, and other elements precipitated by hydrothermal activity. A serpentine sequence in the middle of the sediment-core is of turbiditic origin, inferred from high Mg, Ni, and Cr concentrations. Platinum group elements (PGE) in the serpentinitic sediments were fractionated during the alteration of peridotite. In the hydrothermal sediments PGE are partially enriched.

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Section: Core 95supporting

confidence: 85%

Sediments and Their Geochemistry, Hess Deep

Eckhardt¹,

Puchelt²

1996

Proceedings of the Ocean Drilling Program, 147 Scientific Results

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“…Similar results have been obtained by Thomassin and Touray (1982) and Crovisier et al (1982Crovisier et al ( , 1983Crovisier et al ( , 1985 for basaltic glass altered in seawater. Crovisier et al (1982) have observed the crystallization of hydrotalcite after 20 days of alteration of the basaltic glass in seawater at 50~ They also showed that the crystals were covered by a silico-alumino-magnesian gel whose composition evolves to a saponite (480 days) 9 The association of hydrotalcite with saponite has also been observed by Schmitz et al (1982) in marine sediments from the Galapagos rifts, and by Larsen et al (1991) for basaltic glass altered experimentally in deionized water. Thomassin (1984) studied the transformation of hydrotalcite to smectite during the alteration of basaltic and andesitic glasses in seawater.…”

Section: Discussionmentioning

confidence: 93%

Formation of Hydrotalcite-like Compounds During R7T7 Nuclear Waste Glass and Basaltic Glass Alteration

Abdelouas

1994

Clays and clay miner.

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Abstract--Alteration experiments have been performed using RTT7 and synthetic basaltic glasses in MgC1E-CaClz salt solution at 190~ The duration of experiments ranged from 0.25 to 463 days. The alteration products were studied by Scanning Electron Microscope (SEM), Scanning Transmission Electron Microscope (STEM), X-ray diffraction (XRD) and Electron Spectrometry for Chemical Analysis (ESCA).For both glasses, the early alteration product is a hydrotalcite-like compound [MgrAlzCO3(OH)~6' 4H20] in which HPO42 , SO42-and C1-substitutes for CO32-. The measured basal spacing is 7.68 A for the hydrotalcite formed from R7T7 glass and 7.62 ~ for the hydrotalcite formed from basaltic glass which reflect the high A1/A1 + Mg ratios x (0.34 -< x -< 0.46). The chemical microanalyses show that the hydrotalcite is subsequently covered by a silica-rich gel which evolves into saponite after a few months. These results support the use of basaltic glasses alteration patterns in Mg-rich solution, to understand the long-term behavior of R7T7 nuclear waste glass.

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“…Low temperature overprinting and weathering of serpentine assemblages is marked by the presence ofMg-rich clays minerals (predominantly smectite, sepiolite and palygorskite), Fe-oxides, hydroxides, and carbonate minerals [Schmitz et al, 1982;Bonatti et al, 1983;Karpofj et al, 1989]. Oxygen isotope analyses of late-stage aragonite in veins and serpentine matrix consistently indicate ambient seawater temperatures «10°C).…”

Section: Mineralogical and Chemical Consequencesmentioning

confidence: 99%

Serpentinization of oceanic peridotites: Implications for geochemical cycles and biological activity

Früh-Green

Connolly

Plas

et al. 2004

Geophysical Monograph Series

197

192

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Ultramafic rocks are a major component of the oceanic lithosphere and are commonly exposed near and along slow-and ultra-spreading ridges and in other tectonically active environments. The serpentinization of mantle material is a fundamental process that has significant geophysical, geochemical and biological importance for the global marine system and for subduction zone environments. Mineral assemblages and textures are typically complex and reflect multiple phases ofalteration, deformation and veining during emplacement, hydrothermal alteration, and weathering. In this paper, we review mineralogical and geochemical consequences of serpentinization processes in oceanic upper mantle sequences in different tectonic environments and discuss the relationship between serpentinization and fluid chemistry. We present phase equilibria that provide models for interpreting mineral-fluid relationships in oceanic serpentinitesand allow the simultaneous evaluation ofthe conditions for redox, hydration and carbonation processes. These models predict that serpentinization reactions are sensitive to Si content of ultramafic rocks and that serpentine phases have an upper stability limit of~450°C, where H 2 0-rich fluids will be dominant. More pervasive serpentinization commences with olivine breakdown reactions below~425°C and leads to progressively more reduced fluids with decreasing temperature. Our calculations indicate that carbonates may have extensive stability fields in CH 4 -rich fluids in Si-deficient systems and that they may be significant in generating reducing conditions. Ifmethane formation driven by serpentinization is common, its contribution to the carbon cycle in submarine biogeochemical systems may be substantial. Serpentinization may thus be an important process in sustaining diverse microbial communities in subsurface and near-vent environments and has consequences for the existence of a deep biosphere.

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Hydrothermal serpentine in a Hess Deep sediment core

Cited by 19 publications

References 8 publications

Sediments and Their Geochemistry, Hess Deep

Sediments and Their Geochemistry, Hess Deep

Formation of Hydrotalcite-like Compounds During R7T7 Nuclear Waste Glass and Basaltic Glass Alteration

Serpentinization of oceanic peridotites: Implications for geochemical cycles and biological activity

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